Today's cellular networks are single-vendor systems with proprietary switch/cell-site interfaces that constrain network operators to grow by purchasing equipment from the same vendor that provided their initial equipment.
With dual-vendor capability, network operators can flexibly provide enhanced services by having the original vendor upgrade the existing system or by having another vendor install a new system which is phased in with the existing system.
Since the interface of a base station to a Mobile Telephone Switching Office (MTSO) is proprietary to that vendor, the introduction of a new network by another vendor often requires the installation of all new base stations and switching offices. Cellular network operators in major service areas are reluctant to completely replace their existing vendor's equipment with a new vendor's equipment. The network operators can perceive that a complete replacement would be too costly and too risky to undertake. Further, their system would remain a single vendor network. In order to make the transition as cost effective as possible, the new system must therefore operate in tandem with the old system. This is accomplished by having the new network overlay the old one.
However, since the two networks are incompatible, some problems can arise with call handling between subscribers. Each switching office will often have to handle calls according to the source, destination of each call and of course, the type of subscriber. As the cellular business matures, enhanced services will be more commonly available, and thus two types of subscribers can be identified in the network. Subscribers can be divided into premium or non-premium. The terms are used to differentiate between, for example, centrex integrated subscribers and subscribers to basic only cellular service. In this instance, basic and analog cellular subscribers are referred as non-premium, whereas centrex subscribers are referred to as premium subscribers. Thus, if a call originates from a non-premium subscriber, it is processed by the original switch.
Similarly, if a call is directed to a non-premium subscriber, the call is still processed by the original switch. However, if a call originates from a premium subscriber, it will be handled by the new switch.
Thus, if a new vendor equipment is to co-exist with the original vendor's equipment, subscribers must perceive no significant reduction in service quality or availability and cellular network operators must not be required to replace undepreciated capital equipment where it can be avoided.
There is accordingly a need for a system and a method for enhancing an existing cellular network such that a new system can operate in tandem with an existing cellular network without disrupting service to existing subscribers and without requiring the replacement of existing equipment.